Numerous medical procedures require intracranial entry through the skull to treat tissue in the interior of the skull. Examples of such endoscopic procedures include endoscopic tumor biopsy, tumor evacuation, stroke treatment, treatment of intracranial cysts, hydrocephalus therapy, and others. All such procedures require a safe apparatus and method for accessing the interior of the skull. Many of the procedures also require removal and reentry of devices into the operative field. And all such procedures require safe handling of the apparatus and devices throughout the procedure.
Among the foregoing examples of medical conditions, stroke is a significant cause of disability and death, and a growing problem for global healthcare. More than 700,000 people in the United States alone suffer a stroke each year, and of these, more than 150,000 people die. Of those who survive a stroke, roughly 90% will suffer long term impairment of movement, sensation, memory, or reasoning, ranging from mild to severe. The total cost to the U.S. healthcare system is estimated to be over $50 billion per year.
Stroke may be caused from a blockage in a cerebral artery resulting from a thromboembolism (referred to as an “ischemic stroke”), or by a rupture of a cerebral artery (referred to as a “hemorrhagic stroke”). A thromboembolism is a detached blood clot that travels through the bloodstream and lodges in a manner that obstructs or occludes a blood vessel. Roughly 80% of strokes classified as ischemic, with the remaining 20% classified as hemorrhagic.
Hemorrhagic stroke results in bleeding within the skull, limiting blood supply to brain cells, and placing harmful pressure on delicate brain tissue. Blood loss, swelling, herniation of brain tissue, and pooling of blood that results in formation of clot mass inside the skull all rapidly destroy brain tissue. Hemorrhagic stroke is a life threatening medical emergency, for which improvements in treatment are evolving. An example of treatment of stroke includes the therapeutic administration of high frequency, low intensity ultrasound, referred to as trans-cranial Doppler (TCD). An exemplary procedure involves creation of a bur hole in the skull, and introduction of a wand that can deliver ultrasound therapy. The ultrasound therapy disrupts and removes clots, thereby immediately reducing the dangerous pressure exerted on vital brain tissue. Combined with visualization and aspiration, the therapy has been shown to safely treat hemorrhagic stroke. Other cerebral disorders may also benefit from the administration of high-frequency, low intensity ultrasound, or TCD. Examples include dementia, head trauma, intracranial hematoma, Alzheimer's, and other abnormalities.
In order to safely administer TCD, the surgeon and other clinicians must introduce the ultrasound wand and/or aspiration wand through a burr hole and into the skull. The wand must be safely manipulated throughout the procedure. Among other safety concerns, the surgeon must be aware of the depth of penetration of the wand into the skull. In addition, it is desirable to visualize the lateral and medial orientation of the wand within the skull. Visualization of surrounding structures may be difficult due to the limited space of the burr hole. Additionally, because many pieces of equipment, both large and small, are involved in the procedure, a clinician may be required to leave an endoscope in place in order to made adjustments to or otherwise manipulate other devices, and to remove devices and reenter the operative field with an alternative device. Therefore, it is desirable to improve the apparatus and method by which the wand is introduced through the skull, the method by which reentry is achieved, and the apparatus and method by which the access device is stabilized throughout the procedure.